1. Field of the Invention:
This invention relates in general to flowmeters, and particularly to an acoustic flowmeter for application where high reverberation may be present.
2. Description of the Prior Art:
Flow measurement systems utilizing the propagation of acoustic energy through the fluid have demonstrated that volumetric flow, even with badly distorted velocity distributions can be measured to a high degree of accuracy. One such system which is described in U.S. Pat. No. 3,564,912 is based on time measurements of acoustic pulses propagated in opposite directions across the fluid medium. Measurements taken in several acoustic paths are combined according to a numerical integration technique to compute volumetric flow rate.
The acoustic transducers for such multi-path systems are generally enclosed in a housing and acoustic propagation takes place through an acoustic window of the housing. In some situations, such as computing volumetric flow rates of high temperature liquids the acoustic window is relatively thick thus causing a reverberation problem. Reverberation is the ringing which the transducer detects as a result of its own excitation. This reverberation can distort the received signal from the opposed transducer along the acoustic path so that its time of arrival, needed to compute volumetric flow rate, is inaccurately detected. If the magnitude of the reverberation is large enough, the receiver apparatus can even mistake it for a received signal, which results in erroneous time data measurements.